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Biomedical subjects

A Graybiel

Publications and source records attributed to A Graybiel.

At least 19 recordsLinked to original sources
PubMed1991

Altered sensorimotor control of the body as an etiological factor in space motion sickness.

Exposure to nonterrestrial force levels affects the activity of gravitoinertial force sensitive receptors of the body, both of labyrinthine and nonlabyrinthine origin. It also disrupts the normal patterning of motor control of body orientation and movement. The patterns and levels of muscle innervation necessary to achieve particular body configurations and to bring about particular body movements are greatly affected by background force level and body orientation relative to the force vector. The present studies demonstrate that such altered sensorimotor control of head and body posture along with altered vestibulomotor control are evocative of motion sickness. This observation has explanatory significance both for space motion sickness and the re-entry disturbances that occur after prolonged spaceflight.

Gravitation↗
PubMed1987

Asymmetric otolith function and increased susceptibility to motion sickness during exposure to variations in gravitoinertial acceleration level.

Von Baumgarten and his colleagues (23,24) have suggested that asymmetries in otolith function between the left and right labyrinths may result from differences in otoconial mass and could play a role in space motion sickness. Such asymmetries would be centrally compensated for under terrestrial conditions but on exposure to weightlessness the persisting central compensation would produce a central imbalance that could lead to motion sickness. We have used ocular counterrolling as a way of measuring the relative "efficiency" of the left and right otoliths and have compared the ocular counterrolling scores of individuals with their susceptibility to motion sickness during passive exposure to variations in Gz in parabolic flight maneuvers. The experimental findings indicate that large asymmetries in counterrolling for leftward and rightward body tilts are associated with greater susceptibility to motion sickness in parabolic flight.

Acceleration↗
PubMed1987

Treatment of severe motion sickness with antimotion sickness drug injections.

This report concerns the use of intramuscular injections of scopolamine, promethazine, and dramamine to treat severely motion sick individuals participating in parabolic flight experiments. The findings indicate that a majority of individuals received benefit from 50-mg injections of promethazine or 0.5mg-injections of scopolamine. By contrast, 50-mg injections of dramamine and 25-mg injections of promethazine were nonbeneficial. The use of antimotion drug injections for treating space motion sickness is discussed.

Dimenhydrinate↗
PubMed1987

Head movements in low and high gravitoinertial force environments elicit motion sickness: implications for space motion sickness.

Astronauts report that head movements in flight tend to bring on symptoms of space motion sickness (SMS). We evaluated how head movements in pitch, yaw, and roll--made both with normal vision and eyes-occluded--affect susceptibility to motion sickness in the zero G phase of parabolic flight maneuvers. The findings are clearcut: pitch head movements are most provocative, yaw least provocative, and roll intermediate. Susceptibility is greater with normal vision than with eyes occluded. The same susceptibility pattern emerged for head movements in the 1.8-2.0 G phase of parabolic flight. These experiments suggest that SMS is not a unique nosological entity but, rather, is the consequence of exposure to nonterrestrial force levels. Head movements during departures in either direction from 1 G elicit symptoms. This implies that, rather than speaking of "space motion sickness," it would be more appropriate to think in terms of "nonterrestrial motion sickness."

Gravitation↗
PubMed1986

The effective intensity of Coriolis, cross-coupling stimulation is gravitoinertial force dependent: implications for space motion sickness.

Coriolis, cross-coupled angular acceleration stimulation readily induces motion sickness under terrestrial conditions. Nevertheless, the Skylab astronauts, when tested with such stimulation in-flight, were insusceptible even though each had been susceptible pre-flight. It is unclear whether this decreased susceptibility was the consequence of in-flight adaptation or in part the result of immediate changes in sensory-motor and vestibulo-motor function that occur during exposure to microgravity conditions. To evaluate this issue, we have tested individuals both in the high and low force phases of parabolic flight maneuvers using constant levels of Coriolis, cross-coupled stimulation. Our findings indicate that 1.) subjects are less susceptible when tested in 0 G than +2 Gz; 2.) the perceived intensity and provocativeness of Coriolis stimulation decreases in 0 G and increases in +2 Gz relative to +1 Gz baseline values; and 3.) changes in the apparent intensity of Coriolis stimulation occur virtually immediately when background gravitoinertial force level is varied. These findings explain in large part why the Skylab astronauts were refractory to motion sickness during Coriolis stimulation in-flight. The general implications for space motion sickness are discussed.

Coriolis Force↗
PubMed1986

Sudden emesis following parabolic flight maneuvers: implications for space motion sickness.

Episodes of emesis unaccompanied by the usual prodromal signs of motion sickness have been reported by astronauts in the space shuttle program (10). Such reports have raised the issue whether space motion sickness has different characteristics from terrestrial motion sickness. We present evidence here from parabolic flight experiments that sudden vomiting can occur in response to a provocative vestibular stimulus even when no premonitory symptoms are being experienced. Accordingly, in chronic exposure conditions, the absence of prominent signs or symptoms of motion sickness does not necessarily mean an absence of sensitization.

Aerospace Medicine↗
PubMed1986

Head movements in non-terrestrial force environments elicit motion sickness: implications for the etiology of space motion sickness.

Space motion sickness has become an operational concern in manned space flight. Considerable evidence exists that head movements in free fall, especially pitch movements, are provocative until adaptation occurs (3,4,8,9,11,17,18,22,26). The question arises whether space motion sickness is an unique nosological entity or is due to body movements in a nonterrestrial force environment, a force environment for which the body's dynamic sensory-motor adaptions to 1 G are no longer appropriate (14,16,18-21). To evaluate this issue, we had subjects make controlled head movements during exposure to high gravitoinertial force levels, 1.8-2.0 G, in parabolic flight maneuvers. Head movements in pitch with eyes open were most evocative of motion sickness, yaw movements with eyes covered were least provocative. This pattern is identical to that which occurs when the same types of head movements are made in the free fall phase of parabolic maneuvers (17,18). It appears that space motion sickness is the consequence of prolonged exposure to a non-terrestrial force background rather than of exposure to free fall per se.

Adult↗
PubMed1986

Cardiovascular epidemiology, exercise, and health: 40-year followup of the U.S. Navy's "1000 aviators".

The interrelationship of aging, performance, and stress modification has been the subject of investigations in the U.S. Navy. Beginning in 1940, a study of 1,056 student and instructor pilots lowered previously high attrition rates in training by emphasizing both physical and psychological screening. After World War II, when 208 pilots in the group died, followup studies of the survivors were conducted in 1951, 1957, 1963, 1969-71, 1977, and 1980-81. In February 1981, 715 questionnaires were mailed to known survivors, with 500 replies subsequently analyzed. Additionally, 114 of the respondents who had previously been examined during 1969, were again examined in 1980-81; those individuals were markedly different in their lifestyle, particularly in exercising regularly, abstaining from cigarette smoking, and drinking alcoholic beverages moderately, as contrasted to 28 aviators also examined in 1969 who died in the interim. Healthy lifestyle may alter cardiovascular risk, preventing premature death.

Aerospace Medicine↗
PubMed1984

Elicitation of motion sickness by head movements in the microgravity phase of parabolic flight maneuvers.

During parabolic flight maneuvers in a Boeing KC-135 aircraft 44 college students were tested for motion sickness susceptibility. These subjects were categorized as 1) insusceptible, 2) moderately susceptible, or 3) highly susceptible to motion sickness during exposure to varying gravitoinertial force levels. After categorization, they were tested in the microgravity phase of parabolic flight to see how three types of head movements affected their baseline susceptibility. The head movements evaluated included side-to-side swivel, shoulder-to-shoulder roll, and front-up head and trunk movements; each type of head movement was used on a separate test day for eyes-open and eyes-covered conditions. Ten cycles of head movements were made in each parabola until a motion sickness endpoint, nausea, was reached or 40 parabolas had been completed. All types of head movements significantly increased susceptibility for subjects in all categories; eyes-open conditions were always more stressful than eyes-closed for each kind of head movement. These findings show unequivocally that natural head movements in microgravity can elicit symptoms of motion sickness. They suggest that head movements play an important etiological role in space motion sickness. In ground based studies where head movements are necessary to elicit symptoms, they are also necessary to elicit adaptation. We describe the use of paced and incremented head movement schedules as a possible way of partially alleviating space motion sickness.

Aerospace Medicine↗
PubMed1984

Clinical testing of the otoliths: a critical assessment of ocular counterrolling.

A test procedure which measures the amount of ocular counterrolling (OCR) of the eyes in response to lateral tilt of the body is considered a means of obtaining objective responses to stimulation of the otolithic receptors in the non-auditory labyrinth of the inner ear. OCR is thought to be the result of changing the orientation of the otolithic maculae relative to the gravitational vector. A special optical system (goniometer) has been devised which enables the observer to obtain a clear image of the subject's eye and to measure OCR responses in degrees and minutes of arc. Although attempts have been made elsewhere to evaluate the clinical significance of such responses, the results have been controversial, and clearly indicate the need for further study in order that OCR may be utilized as a reliable diagnostic tool. Accordingly, a review of the literature is presented, together with preliminary findings at St. Michael's Hospital and recommendations for further research.

Adult↗
PubMed1983

Etiological factors in space motion sickness.

We compared susceptibility to motion sickness during exposure to sudden-stop stimulation as a function of gravitoinertial force level. Our findings show that susceptibility is greatly enhanced, both with eyes-closed and eyes-open, for zero-g and 2-g conditions in parabolic flight compared with 1-g test conditions. The change in susceptibility is likely related to three factors: alterations in vestibulo-ocular function which result from variations in gravitoinertial force level (28,29); the altered pattern of otolithic activity resulting during variations in gravitoinertial force level; and the altered canal-otolith response synergies that result during exposure to gravitoinertial force levels greater or less than terrestrial levels. These factors are shown to be related to the etiology of space motion sickness and to the alterations in performance and vestibular function that are experienced by astronauts during reentry. An explanation is also proposed for the decrease in susceptibility to motion sickness exhibited by the Skylab astronauts inflight and for some period postflight during exposure to cross-coupled angular accelerations.

Adult↗
PubMed1981

Mechanisms underlying modulations of thermal nystagmic responses in parabolic flight.

In six subjects nystagmography was used to compare the responses to cold calorization of one horizontal semicircular canal under ground-based and parabolic flight conditions. On the ground the expected individual differences in primary nystagmic responses were observed; only one subject manifested a brief weak secondary nystagmus. Aloft, the irrigation was carried out in straight-and-level flight prior to a pushover (half-parabola) that initiated a series of four to nine typical parabolas in a modified KC-135 aircraft. Thereafter, the free-fall phases of the parabolas furnished a zero baseline for measuring weight differences in endolymph due to changes in gravitoinertial force. In all subjects a secondary nystagmus was generated in addition to the primary nystagmus during the course of the parabolic maneuvers. The slow phase of the secondary nystagmus rarely exceeded 10 mm per sec. Evidence is presented that secondary nystagmus arises as a direction-specific adaptation effect countering the primary nystagmic response. Three stages were recognizable: first, when primary and secondary nystagmus alternated in step with the high and low force phases of the parabolas; second, after disappearance of primary nystagmus when secondary nystagmus appeared alone and was modulated by the changes in force; and third, when the secondary nystagmus present became independent of the highest gravitoinertial forces generated. Great individual differences were observed, suggesting that with large departures of the cupula from its functional rest position there are large individual variations in rate of restoration.

Adult↗
PubMed1979

Parabolic flight: loss of sense of orientation.

On the earth, or in level flight, a blindfolded subject being rotated at constant velocity about his recumbent long body axis experiences illusory orbital motion of his body in the opposite direction. By contrast, during comparable rotation in the free-fall phase of parabolic flight, no body motion is perceived and all sense of external orientation may be lost; when touch and pressure stimulation is applied to the body surface, a sense of orientation is reestablished immediately. The increased gravitoinertial force period of a parabola produces an exaggeration of the orbital motion experienced in level flight. These observations reveal an important influence of touch, pressure, and kinesthetic information on spatial orientation and provide a basis for understanding many of the postural illusions reported by astronauts in space flight.

Acceleration↗
PubMed1979

Some influences of vision on susceptibility to motion sickness.

Two experiments were performed to evaluate the influence of vision on susceptibility to motion sickness during exposure to constant patterns of vestibular stimulation. The motion profile involved accelerating subjects at 20 degrees/s2 to 300 degrees/s, maintaining them at that constant velocity for 30 s, and decelerating them to a rapid stop in about 1.5 s. The number of stops tolerated by a subject before reaching the motion sickness endpoint served as his score. In Experiment 1, subjects were tested twice with their eyes open and twice with their eyes blindfolded. They tolerated fewer sudden stops when permitted sight of the experimental chamber. In Experiment 2, the effect of having the eyes-open or closed at different stages of the motion profile was evaluated. Having the eyes open during any stage of the test was more stressful than having the eyes closed, but this was especially true during the sudden stops. The findings are discussed in terms of their general implications for understanding a) situations in which vision alone elicits symptoms of motion sickness, and b) situations involving vestibular stimulation where vision heightens susceptibility.

Acceleration↗
PubMed1979

Prevention and treatment of space sickness in shuttle-orbiter missions.

Today it is impossible accurately to predict susceptibility to space sickness of crew members making their first transition into orbit, for want of a ground-based validated model of free fall. Even assuming that space sickness is simply a specific designation for motion sickness that may be experienced in orbital flight (and here agreement is not general), preventive therapy poses difficult problems because, for a priori reasons, either all crew members or none should receive treatment. If all receive preventive therapy, everyone should execute head movements in a programmed manner to ensure rapid adaptation to the environment; at least a large minority will not benefit but rather will experience whatever sideeffects inevitably accompany administration of a drug. If none receive preventive therapy prelaunch, at least a large minority will pose two problems--treatment for acute motion sickness and rapid acquisition of adaptation. Trade-offs will involve the identification of long-acting antimotion sickness drugs for use prelaunch that will be efficacious for at least 90% of those going aloft for the first time and the effectiveness of combining rapid adaptation with treatment of motion sickness. The following report describes recent experiments dealing with these problems.

Adult↗
PubMed1979

Oculogravic illusion in response to straight-ahead acceleration of CF-104 aircraft.

Experimental subjects wore goggles that restricted monocular vision to a luminous line fixed relative to the head, and they were exposed on one occasion to a straight-ahead acceleration of an aircraft and on another occasion to a tilting chair. The magnitude of change of direction of the resultant accleration was the same on both occasions, but the perceived movement of the luminous line from the two stimuli was very different. In response to the aircraft stimulus, the oculogravic illusion was experienced and the luminous line was perceived as tilting relative to the subject, in response to the tilting chair stimulus, the line was perceived as remaining fixed relative to the subject. It was concluded that the oculogravic illusion, as experienced in the aircraft (and previously in centrifuges), is a true illusion and not merely a fact of physics.

Acceleration↗
PubMed1979

Rotation at 30 RPM about the A axis after 6 hours in the 10 degree head-down position: effect on susceptibility to motion sickness.

Intraindividual differences in susceptibility to motion sickness were measured in 14 subjects for two conditions of rotation at 30 rpm in the 10 degree head-down position. In one condition, subjects were in the 10 degree head-down position for 6 h prior to the onset of rotation; in the other condition, the delay was only 15 min. In both conditions, there were changes in vital capacity, indicating a redistribution of movable body fluids. Subjects tended to be less susceptible to motion sickness when they were recumbent for 6 h prior to rotation. These results are countervidence for the hypothesis that shifts of body fluid are responsible in large part for the motion sickness elicited in orbital space flight.

Aerospace Medicine↗